1. Field of the Invention
The present invention relates to a side shifting attachment for fork lift trucks, more particularly to an improvement in the mechanical construction of a side shifting attachment which will enhance the operational performance and increase the working life thereof.
2. Description of the Prior Art
A conventional fork lift truck with side-shiftable fork tines is disclosed, for example, in PCT application No. PCT/JP79/00218 of the same assignee, now WO 80/00434. In this type of construction, the side-shiftable fork tines are mounted by means of a conventional side shifting attachment on a lift bracket moving up and down on uprights arranged on a foremost end of the truck body, and are moved transversely by a transverse actuator of the side shifting attachment consisting of a well known fluid-operated cylinder. In the conventional side shift attachment, the transverse movement of the fork bar is assisted by rollers, or by a liner, placed between the fork bar and the finger bar attached to the lift bracket. Where a liner is used, a problem arises wherein, when a load is lifted and the upright masts tilted back, the fork bar presses against the finger bar, causing abrasion and wear of the fork bar and finger bar during transverse movement. In an attempt to combat this problem, a gap is left between the finger bar and the fork bar. The width of this gap is determined and maintained by shims inserted between the liner and the fork bar. This construction will be later explained in detail. However, the presence of this gap allows a "rocking" motion to occur when a load is lifted or set down by the fork tines. That is, the fork bar is pushed backward when the fork tines are inserted into, for example, a loaded pallet, and is pulled forward when the fork tines take the weight of the loaded pallet. These actions cause the liner to move accordingly, i.e., cause play between the liner and the fork arm, with the result that the shims are moved out of position, the gap is accordingly widened, and the play is subsequently increased.